Such drives, which are also identified as suspension drives, have been known for some time. German Pat. No. 838 452, for example, discloses a drive of the described type as its subject matter, in which the elastic coupling is formed of a rubber disk which surrounds the wheel-set axle and which is connected on one axial side thereof to a disk-shaped flange secured to the hollow shaft and on the other axial side thereof to a disk-shaped flange which is mounted on the wheel-set axle, for example by a vulcanizing process. All double axle drives of the above-described type are characterized by the elastic couplings not only having to transmit the torque but must also absorb the reaction moment of the motor and must resiliently carry the entire weight of the drive aggregate. In the construction of the elastic coupling, which is discussed here, the rubber is mainly stressed with respect to shear through the weight and the mass forces which occur during driving, namely in a plane, which lies perpendicularly with respect to the wheel-set axle. In order to prevent the drive system for sagging too much with respect to the wheel-set axle, the rubber disk must be relatively thin and hard. However, this increases the negative effects of the shearing stress and the spring action is further worsened in cross direction, thus in direction of the wheel-set axle. A further very important disadvantage is that during an exchange of the rubber disks, which exchange will become necessary, the wheels must be pulled off from the axles.
This disadvantage, which very much interferes with the operation, is avoided by coupling having split rubber or elastic elements, as it is known among others from German OS No. 23 32 281. A hub which is mounted on the hollow shaft and one which is mounted on the wheel-set axle have a plurality of radially outwardly extending arms, which are arranged alternately lying one behind the other and a rubber block being inserted between each two arms. The rubber blocks can be removed individually radially outwardly and can be installed from outside without requiring a removal of the wheels from the axles. This type of coupling is very stiff in the plane which is positioned perpendicularly with respect to the wheel-set axle. In cross direction, it is softer than the construction utilizing the rubber disks, however, the rubber blocks are exposed to a shearing stress. Further disadvantages are the complicated shape of the coupling arms and the resulting machining difficulties and the fact that the rubber blocks receive their initial tension not before the installation, which makes the installation and the demounting more difficult.
Therefore, the basic purpose of the invention is to provide a double axle drive of the above-described type, which does not have the mentioned disadvantages, thus is easy to manufacture and easy to service, and the rubber or elastic elements of which are exposed to no shearing stresses at all or only small shearing stresses.
The purpose is attained by providing a construction for the elastic couplings, wherein with each two coupling halves, one is mounted on the hollow shaft of the gearing arrangement, the other one on the wheel-set axle and both are constructed substantially as rotation-symmetrical members and are connected through circumferentially arranged flexible joint sleeves. For a balanced operating behavior, at least three flexible joint sleeves are needed in each coupling; since the sleeves, however, are, as much as possible, no to be stressed for shear, there should be no less than six flexible joint sleeves in each coupling. Because of the star-shaped arranged rubber or elastic joints, such couplings are also identified as "star coupling".
The connection of the two coupling halves through the flexible joint sleeves can occur so that the one coupling half has radially outwardly directed pins, which receive the flexible joint sleeves in their openings, while the other coupling half is provided with openings, in which the flexible joint sleeves are received on their outer sleeve members.
Various preferable construction possibilities exist for the design of the flexible joint sleeves. Thus it is for example possible to vulcanize in the simplest form a rubber or elastic ring between a metallic inner part and an outer part, which rubber or elastic ring is adjusted in its cross section to the respective operating conditions and material characteristics. To further reduce the shear stress, it is possible for two rubber or elastic rings, with a metallic intermediate ring, surrounding one another concentrically to be vulcanized between an inner part and an outer part. In order to make the coupling stiff in one plane, for example in circumferential direction and in transverse direction thereto, thus in direction of the wheel-set axle, but to permit a soft deflection of the coupling, recesses or openings at certain points in the rubber or elastic rings are advantageous. In order that the tensile stresses which occur during the deflection in the rubber or elastic rings do not lead to a removal of the rubber or elastic rings from the metal parts, the rubber or elastic rings are to be vulcanized in place under initial tension. The initial tension can be increased, when the outer and, if desired, intermediate ring are divided in the area of the openings in longitudinal direction such that they have a semicircular-shaped cross section and are arranged at a radial distance from one another, which corresponds with the desired initial tension. The flexible joint sleeve assumes the round cross section only in the installed condition. The installation process can thereby be made easier, when the flexible joint sleeve is received in an intermediate sleeve. The coupling halves which receive the flexible joint sleeves at their outer sleeve members are divided advantageously in such a manner that the flexible joint sleeves are received on half of the periphery of their surfaces by the actual coupling half and on the other half of their periphery by a ring or the like which is connected to the coupling half. Installation and service works are made easier if the ring is again divided transversely with respect to its axis into two semicircular rings or if in place of a ring which receives all flexible joint sleeves several bearing brackets are provided which are secured to the coupling half. The arrangement of the coupling on both ends of a hollow shaft can be done in such a manner that both couplings are angularly spaced at the same angle from one another or, however, so that they are offset against one another at half the angle between the two flexible joint sleeves.
A double axle drive according to the invention offers with respect to the known construction a whole series of advantages, namely:
The rubber joints are stressed by the torque to be transmitted and by the weight of the motor-gearing-aggregate substantially for pressure and only little for shear.
The exchanging of individual elastic joints can be done without dismantling of the railway truck and without dismantling of the motor, gearing arrangement and/or axles and wheel sets.
At an angular deflection only small return forces occur, which assures a great safety against derailment.
The return forces can be adjusted to the requirements through a suitable design of the elastic joints.